In the display skill field, Liquid Crystal Display (LCD), Organic Light Emitting Diode (OLED) and other panel display skills have been gradually replaced the CRT displays. The OLED possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, fast response, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential flat panel display technology.
The OLED can be categorized as Passive matrix OLED (PMOLED) and Active matrix OLED (AMOLED) according to the driving types. Generally, the AMOLED comprises a Low Temperature Poly-Silicon (LTPS) drive back plate and an electroluminescence layer for being the self-illumination component. The Low Temperature Poly-Silicon possesses higher electron mobility. For the AMOLED, the LTPS material possesses advantages of high resolution, fast response, high brightness, high aperture ratio, low power consumption, et cetera.
A structure of an AMOLED back plate according to prior art is shown in FIG. 1. The manufacture process of the AMOLED back plate generally is:
step 1, deposing a buffer layer 200 on a glass substrate 100;
step 2, deposing an amorphous silicon layer (a-Si) on the buffer layer 200, and using the Laser process to make the amorphous silicon layer to be crystallized and converted to be a polysilicon layer (Poly-Si);
step 3, patterning the polysilicon layer with photo and etch processes to form a first polysilicon section 301 and a second polysilicon section 303;
step 4, deposing an N type heavy doped amorphous silicon layer N+a-Si on the buffer layer 200, the first polysilicon section 301 and the second polysilicon section 303, and implementing the photo process to define the position of the channel 400, and etching to pattern the N type heavy doped amorphous silicon layer N+a-Si for forming a source/a drain 401 on the first polysilicon section 301 and an electrode 403 on the second polysilicon section 303 except an area corresponding to the channel 400;
step 5, deposing and patterning the gate isolation layer 500 on the buffer layer 200, the source/the drain 401 and the electrode 403;
step 6, deposing and patterning a first metal layer on the gate isolation layer 500 to form the gate 601 and a metal electrode 603; the gate 601 is above the source/the drain 401, and partially overlaps with the source/the drain 401 in the horizontal direction;
step 7, sequentially forming an interlayer insulation layer 700, a metal source/a metal drain 801, a flat layer 900, an anode 1000, a pixel definition layer 1100 and a photo spacer 1200 on the gate isolation layer 500, the gate 601 and the metal electrode 603 with deposition, photo and etch processes.
The metal source/the metal drain 801 are electrically connected to the source/the drain 401; the anode 1000 is electrically connected to the metal source/the metal drain 801.
The first polysilicon section 301, the source/the drain 401, the gate 601 and the metal source/the metal drain 801 construct a drive TFT, and the second polysilicon section 303, the electrode 403 and the metal electrode 603 construct a storage capacitor.
The drive TFT of the AMOLED back plate shown in FIG. 1 is a NMOS, the AMOLED panel can occur the phenomenon of image sticking more easily. Besides, the contact resistance between the source/the drain 401 formed with the N type heavy doped amorphous silicon layer N+a-Si and the first polysilicon section 301 is higher, and thus, the conductive current of the drive TFT can be lower, and the source/the drain 401 and the gate 601 partially overlap in the horizontal direction, which can cause the leakage current of the drive TFT to be over high.